Does anyone else think that Kristen was just playing herself?

I am not a troll or a hater, but after seeing this movie, I fail to recognize this 'superb' performance by Stewart, which got her a Cesar award, the French Oscar. I don't know, the way she said her lines, the way she acted, dressed, just seemed normal to me, nothing great about this performance. To me it looked like she made no effort. Just playing Kristen Stewart, using the typical Kristen Stewart clothes, her converse sneakers, her torn jeans, her open checked shirt with a rock band t-shirt underneath, her cigarette. The only difference is the glasses, which I am not sure she wears in real life. I have seen other movies of hers, but then I could buy more into it. Here I saw no effort in her performance. She delivered the lines exactly the same way as if she was in an interview talking about Robert Pattinson back in Hollywood. There was nothing challenging or difficult. Given she plays an assistant to a foreign actress she didn't even speak French, which made it even easier. I guess the competition for the Cesar award last year must have been very bad. Very bland performance. Can someone explain what is so great about her performance?